This invention relates to formulations for sizing paper and more particularly to solutions of polymers of styrene and maleic anhydride for alkaline sizing of paper.
Ammonium salts of polymers of styrene and maleic anhydride dissolved in water are known for use in sizing paper. See, for example, U.S. No. 2,261,169, col. 7, lines 59-61. Sizing is the treatment of paper fibers to improve properties such as ink printability and penetration, gloss, porosity and the like. Alkaline surface sizing wherein polymeric ammonium salt solutions are used with starch or the like as filler is becoming increasingly important to improve the durability of paper over time insofar as reducing its tendency to yellow. Moreover, alkaline surface sizings facilitate using increased filler in the paper substrate and therefore reduced, relatively expensive paper fiber without loss in paper properties. It would be desirable to modify these polymeric solutions used in alkaline sizing to enhance their capability to improve the properties of paper on which they are deposited.